<?php

function isPrime($number)
{
	if ($number == 2 || $number == 3) {
		return true;
	}
	
	if ($number % 2 == 0 || $number % 3 == 0) {
		return false;
	}
	
	$i = 5;
	$w = 2;
	
	while ($i * $i <= $number) {
		if ($number % $i == 0) {
			return false;
		}
		
		$i += $w;
		$w = 6 - $w;
	}
	
	return true;
}

$testPrimes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997];
$testNotPrimes = [4, 6, 10, 12, 14, 15, 21, 22, 24, 25, 26, 27, 51, 52, 60, 62, 63, 64, 65, 66, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 85, 86, 87, 99, 100, 102, 135, 140, 141, 142, 143, 148, 150, 155, 161, 170, 200];

foreach ($testPrimes as $testPrime) {
	if (!isPrime($testPrime)) {
		echo "Algorithm is not working properly. {$testPrime} is a prime, and algorithm returned that it is not.\n";
	}
}

foreach ($testNotPrimes as $testNotPrime) {
	if (isPrime($testNotPrime)) {
		echo "Algorithm is not working properly. {$testNotPrime} is not a prime, and algorithm returned that it is.\n";
	}
}
